PARIS, Jan 16 (Reuters) – France’s plans for a massive expansion of the metro network in and around Paris risk “considerable” cost overruns and may not be ready in time for the 2024 Olympics as planned, the country’s independent auditing body warned on Tuesday.

In a report seen by Reuters, the Cour des Comptes said the so-called “Grand Paris Express”, one of Europe’s biggest infrastructure projects, could cost 38.5 billion euros ($47 billion), more than 12 billion euros higher than the last estimate in 2013.

“The court believes it necessary to warn about the considerable overrun of the projected costs of the Grand Paris Express project,” it said.

The court said it also had “serious doubts” about the project’s ability to open in time for the 2024 Olympics, which the French capital was awarded last September.

The Grand Paris Express project, decided in 2010 by former president Nicolas Sarkozy, aims to better link Paris suburbs to the city proper and to each other with four new lines of mostly underground automatic trains.

The 200 km (124 miles) of new metro lines – almost twice the length of London’s future Crossrail railway line – would double the size of the existing network, which was mostly built at the turn of the last century.

The court said the cost overruns will have a “significant” impact on public finances over the next five years.